Sound signal apparatus



Dec. 29, 1942.

J. R. M K AY scum) SIGNAL APFARATUS Filed March 14, 1958" 5 Sheets-Sheet 1 INVENTOR ATTORNEYS Dec; 29, 1942. J. R. MacKAY 2,306,819

' soUND smm, APPARATUS F iled March I4, 1938 5 Shee ts-Shet 2 INVENTOR 65 66 @TTORNEYS Dec. 29,1942. J. R. MacKAY 2,306,819

souun SIGNAL APPARATUS Filed March 14, 1938 5 Sheets-Sheet 3 Dashpot I00 INVENTOR ATTORNEYS BY orp, Kwv W Y Dec. 29., 1942. J. R. acKAY 2,306,819

SOUND SIGNAL APPARATUS Filed lunch 14, 1938 s'sheets-sh t 4 Dec. 29, 1942; J, MacKAY SOUND SIGNAL APPARATUS :5 Sheets-Shet 5 Filed March 14, 1958 T M I INVENTOR ATTORNEYS ion, by the armature.

Patented Dec. 29 194-2 2,396,819 soUNn SIGNAL APPARATUS John R. MacKay, West Caldwell, N. J., asslgnor to Wallace & Tiernan Products, In c., Belleville, N. J., a corporation of New Jersey 7 Application March 14, 1938, Serial No. 195,893

20 Claims.

This invention relates to sound signal appa- 'ratus, and more particularly to signalling or alarm devices of electrically operated type, such as horns, and to control means for signalling apparatus of the character stated. An especially advantageous use or embodiment of the invention is in ,fog horns, wherein ruggedness, power of sound, and dependability over long periods of time are important criteria. Such horns are often used on floating buoys, and the requirements of a satisfactory horn for such use are particularly severe. All parts must be of a type suitable for use on buoys, where they will be subject to continuous operation, exposure to the ele-' ments and to frequent submergence, and to operation at all angles due to the swinging and listing of the buoy. As buoys are frequently collided with all parts of the horn and program mechanism must be of such construction that they will not. be damaged or operation affected by any jar or bump which the buoy may receive, other than one where the horn or mechanism is actuallyhit and damaged in consequence. It is a common requirement of horns so'used, that they must sound from two to four blasts of about one second per minute, and that this operation is continuous for 24 hours per day for each day of the year.

In general, sound signals such as fog horns have comprised an electromagnet, an armature, a diaphragm associated with the armature, and make-and-break contacts operated, buzzer fash- Certain difllculties, however,' have been found with devices heretofore known or available. For example,- the pitch of the horn depends on the stiffness of the diaphragm, and inversely on the weight of the arma ture; and attempts to obtain a pitch high enough for good carrying quality haveeither required a sacrifice of power or involved a tendency to break tory power and pitch characteristics, which is at the same time highly reliable and adapted for operation over extremely long periods of time without even partial failure or appreciable reduction in its output due to wear.

Another object is to provide a sound signal device having novel and improved means for automatically controlling the device and for operating it, for example, at regular intervals and with uniformity of power and efficiency; other objects being to provide more satisfactory contact structures in sound signals, and likewise efficient arrangements for preventing or greatly reducing wear of the contacts.

A still further and notably important object is to provide an improved structure in sound signal devices whereby the amplitude of vibration may be accurately adjusted or set, and a like important object is the provision of novel means for maintaining a constant amplitude of vibration on the part of the relatively stiff diaphragm used,

when flexed with sufficient amplitude to create a powerful signal. Furthermore, although it is usually desirable to space the diaphragm relatively far away from the armature, with a connecting member, it has been found that the spring then employedto support the end of the armature distant from the diaphragm, is very apt tobreak upon continued vibration of otherwise desirable power.

The present invention is particularly designed to remedy one or more of these and other difilculties inherent in prior art'devices, and a further object of the invention is to provide appaover long periods of operation, or for making automatic adjustment in response to decreased amplitude or effects concomitant therewith.

Another object is to provide novel interlocking means for synchronously controlling both the signal characteristic and a reversal of current flow through the horn contacts and associated current controlling contacts, periodically and without conflict between the signal current controlling and current reversing means.

Other objects are to provide, relative to fog horns and like signal apparatus: an improved and long-wearing diaphragm structure; a simpler and more efficient assembly of vibrating parts; and generally sturdier and more reliable arrangement of operating and control elements.

Other objects and advantages include those which are hereinafter stated or apparent, or which are incidental to the invention. The nature of the latter will be conveniently explained by reference to the following description and accompanying drawings, which set forth, by way of example, certain presently preferred embodiments of the invention.

In the drawings:

Fig. 1 is an elevation of a complete fog horn and control unit embodying the invention;

Fig. 2 is an enlarged longitudinal section of the horn and its operating parts;

Fig. 3 is a plan of the upper end of Fig. 2;

Fig. 4 is a section on line 4-4.0! Fig. 2;

Fig. 5 is a general wiring diagram;

Figs. 6 to 10 inclusive are diagrammatic views of various modifications of the invention;

Fig. 11a is a diagrammatic view of an alternative structure of certain elements in Fig.

Fig. 11b is a perspective view of a generator device shown diagrammatically in Fig. 11a; and

'Fig. 12 is a diagrammatic view of a further modification of the invention.

As generally shown in Fig. 1, the sound signal device and its associated control instrumentalities may be conveniently combined in a single unit; comprising an open-mouthed trumpet or bell 20, bolted to a housing 2| for the horn-driving elements, the housing being in turn secured to a case 22. The latter encloses an electric motor unit 23, having associated program cams and contacts as hereinafter described, and also encloses fuses and a relay 24 for operating the horn. Certain adjustable elements of the horn proper, generally designated 25, may be disposed within the casingZZ, and the face of the latter shown in Fig. 1 may conveniently comprise a door or cover plate hinged (at 26a) to open upon release of the toggle bolts 26, for access to the enclosed parts, including the elements 25. For convenience of access and adjustment the parts generally designated 23 and 24 are mounted on the inside of the door and are swung out of the casing with it. It will be understood that particularly where the apparatus is to be used at sea or off shore, as on a floating buoy, or where it is otherwise to be exposed to weather o moisture, the entire assembly of casing 22, housing 2| and the inner end 21 of bell 20, must be thoroughly water-tight. To that end, the peripheries of diaphragms, interposed gaskets, and other joined elements, may be embedded in waterproof plastic material, such as glyptol lacquer. A cone-shaped or other deflector 26a may be disposed below the mouth of bell 26, and may be vertically adjusted on its supporting bolts to permit some change of the resonant length of the air column in the bell or trumpet.

Referring now to Figs. 2 to 4 inclusive, there is supported within the housing 2| an electro-magnet generally designated 36, and comprising a laminated iron or preferably laminated steel core, having a central pole 3| and flux-returning portions 32 terminating in the same plane as the pole 3|, to provide adjacent pole elements of opposite polarity, for powerful signal action; the magnet winding 33 is conveniently disposed about the central pole member 3|, as shown. The central portion of the field core, viz., the pole member 3|, is conveniently provided with a longitudinal hole or tunnel, to admit a tubular shaft or connecting member 34 which is part ofothe vibrating substantial space; the inner diaphragm group 35 conveniently comprises three diaphragms 35a spaced slightly apart, while the group 36 comprises two diaphragms 36a, likewise spaced slightly apart. The diaphragms are peripherally rethere are provided two 1 groups of diaphragms 35 and 36, separated by a tained to the housing 2| by a plurality of bolts 31, circumferentially spaced around the assembly. Thin supporting rings 38 serve to space the diaphragms within the respective groups, and the groups are separated by a cylindrical spacing member 39, and all parts are preliminarily retained in place by the bolts 31 and securely clamped to the housing 2| by a plurality of bolts 46 spaced around and passing through a flange on the bell or trumpet 26, whereby the latter is also clamped against the diaphragm assembly and housing 2|. It will be noted that the annular face of the bell which abuts against the diaphragm assembly, specifically the outer diaphragm group 36, is provided with a relatively wide annular groove 4|, so that the area of contact between the bell or horn proper, and the diaphragm assembly, is confined to a pair of spaced, concentric and'relatively narrow annular paths 42 and 43, affording an extremely close fit of the bell 20 against the diaphragm assembly and the housing.

The several diaphragms 35a and 36a are centrally pierced by and secured to a sleeve 45, having its interior in threaded engagement with the outside of tube 34. Intermediate the several diaphragms of each group on the sleeve 45, central spacing washers 4502 are provided for accurately spacing the diaphragms at the center, and when the assembly is made up, the ends of the tube 45 are advantageously upset or riveted against the heavy terminal washers 45b, Whereby each diaphragm group is firmly secured against its corresponding shoulder 450 on the tube 45; The opposite end of the tube 34 on the other side of the electro-magnet 30, is seated in an armature 46, which comprises laminations of iron or preferably steel in the same plane as laminations of the field core 3|, 32, and which is disposed in proximity to the poles of the latter. A long bolt 41 extend through the tubular shaft 34 int threaded engagement with a member 48, which provides an extension for the shaft 34 beyond the armature 46, and into which the bolt 41 may be tightened so that the head of the latter engages a lock washer 49a against a large knurled washer 49 which is keyed to and abuts the end of sleeve 45, and the sleeve is locked in adjusted position on the shaft 34, Before the bolt 41 is tightened, the knurled washer 49 may be turned t screw the sleeve 34 longitudinally in the sleeve 45 so as to adjust the air gap between armature 46 and the core 3|, 32.

It will be understood that in the preferred construction shown, the passage of shaft 34 through the hole in pole 3| (strictly speaking, through the tube 34a) is completely freei. e., there is no contact anywhereand indeed the shaft is entirely clear of supporting engagement or abutment at any point above the diaphragm assembly as seen in Fig. 2. That is, the spaced groups of diaphragms 35 and 36, serve alone, and very satisfactorily, to support the remainder of the vibrating assembly, including shaft 34 and the driving armature 46. Frictional, spring or other supplementary supports for the. vibrating instrumentalities are thus entirely eliminated, and at the same time the arrangement is such that the respective positions of the various parts carried by or connected to the shaft 34 may be readily adjusted and the parts accurately locked in adjusted position. Furthermore, by virtue of the inclusion of a plurality, and preferably a multiplicity, of spaced parallel diaphragms which a e each relatively thin, an eminently desirable stiffness is obtained for the diaphragm structure without tendency of breakage on the part of its individual constituents. In other words, the diaphragm arrangement may safely be stiff enough to provide a. desirably high pitch, although a relatively heavy armature 46 is used to obtain powerful driving action, For example, a horn of the type shown has been satisfactorily constructed to produce a note of 205 to 210 cycles per second, yet strong enough to be heard clearly for several miles, under average listening conditions.

The outer end of the member 48 carries one contact 50a of a pair of contacts generally designated 50, and arranged to open or close in accordance with longitudinal displacement of the shaft 34. The other contact 50b of the set is mounted von a spring conveniently secured to but insulated from the casing 22. To avoid flexing of its end portion, the spring 5| may have a reinforcing plate, or it may preferably have integral upwardly turned ears 52 along its sides, which not only reinforce the end-of the spring, but enlarge its end area so as to prevent breakage adjacent the hole where contact 50b is mounted. The contact 501), moreover, preferably has a tubular shank 50c whereby it is riveted in the ter and carrying a lock nut 480, so that the contact may be locked in position of best alignment with contact 501).

The instrumentalities hereinabove described are also diagrammatically shown at the upper part of Fig. 5, except that for purposes of simplicity the diaphragm structure is shown as a single diaphragm member 50. It will here be seen that the internal wiring arrangement of .the horn is simply such that the winding 33 is source of current, such as a storage battery, is

connected across the terminals 6|. Contacts 50 are normally in closed position, and the winding 33 being thus energized, the armature 46 is attracted by the field poles 3|, 32. The contacts hole of the spring, so that when the-contact heats up-in/use, the shank may expand inwardly and avoid straining the spring 5|. The outer end of the spring 5| extends beyond the contacts and is adapted to strike an anvil member 53 which is thus arranged to limit the motion of the spring downward as seen in Fig. 2. The anvil member 53 advantageously comprises a worm gear mounted on a shaft which is threaded into a cross member 54 that is suitably insulated from the housing 2| and case 22 (it being understood that the housing and case are conveniently bolted together at 55a, as shown). The lower end of the worm gear shaft ha'sthreaded on it a leaf spring 53a, which has its ends abutting the under side of the member 54 and which strongly biases the worm gear in a downward direction to prevent play and-chatter. A pin 53b, carried by member 54, engages a slot in the leaf spring 53a'to prevent rotation of the latter.

A worm 55 is journaled in suitable supports on the member 54, for rotative engagement with the gear 53, and is provided with a milled or toothed wheel 56, and an operating shaft 51 having a slotted head. A check spring 58 releasably engages the teeth of the wheel 56; and the arrangement is such that by inserting a screw driver in the slot of member 51, and turning the same, the worm 55 will rotate the gear 53 and raise or lower the upper or anvil face of the latter with respect to the outer end of spring 5i.

' During such adjustment the check 58 clicks over the teeth of wheel58, but serves to lock the assembly in any adjusted position. The slotted shaft or head 51 is preferably insulated from the assembly of wheel 56 and worm 55, so as to prevent electric shock to the operator making adjustments, or inadvertent grounding should his 'screw driver also touch the metal casing. Pref erably both the anvil 53 and contactsprin g 5| are of hardened steel construction, for maximum wear resistance. It may now be explained that the parts generallly designated 25 in Fig. 1 may comprise the elements 51, 55, 53, 5| and 50, which. are thus readily accessible, through the door of,

casing 22, for inspection and adjustment.

It will be understood that the lower contact 50a may be mounted for vertical adjustment in membcr 48, as by a shank threaded, into the lat- '7 armature 46.

remain closed, i. e., the spring 5| follows the downward displacement of the armature 46 (Fig. 5), until the outer end of the spring strikes the anvil 53. The.downward stroke of the armature and diaphragm assembly 46, 50 then continues, as will be well understood; and upon the return stroke (initiated by the energy stored in the diaphragm), contacts 50 again close, and under a presently preferred adjustment with respect to the natural period of the vibrating system, the spring 5i is flexed back to and past its original position as shown in Fig. 5, and the cycle is repeated. Other things being equal (except the current consumption) the amplitude of diaphragm vibration is dependent upon the space 52 intermediate the upper surface of anvil 53 and the outer end of spring 5| in its neutral or rest position; that is, the wider the space the longer the contacts 50 are closed during each stroke, and the greater the force exerted on the It will now be seen that the described horn structure, including the worm 55 for varying the position of anvil member 53 with respect to the spring 5|, is provided with effective means for adjustin the amplitude of diaphragm vibration, so as to obtain and maintain the desired amplitude at all times and without excess current consumption.

When the horn is used for marine signalling purposes, for which it is notably adapted, it must draw a relatively substantial current in order to produce a signal sufliciently powerful to be heard, say, for several miles. Undersuch circumstances-for example, where the, horn is located and hooked up as on a floating buoy, to operate automatically at frequent interv'als-long continued use is apt to wear down the surfaces of L the rapidly operated contacts5li (event-thou a condenser 63 or a condenser-resistor funit, is connected across them, as 'shown' in-ijFig'; 5), or

more particularly to carry metal from: cnelcontact to the other, thus causing thefpitting-ofone contact and the building up of the other Con act so as to disturb their parallelism and their reladucing the wear on the contacts;

It has been explained-hereinabov'e that the casing 22 may contain a motor 23, together with ,each revolution of cam 61.

an associated cycling mechanism and a horn controlling relay 24. As shown diagrammatically in Fig. 5, the electric motor 23, which may be energized. from a pair of storage batteries 65 and 66, connected in series, is adapted to drive a pair of cams 61 and 68. Although other motors may be satisfactorily employed in many cases, I prefer to use a motor of the type described and claimed in United States Patent No. 1,985,357, to Charles F. Wallace, for Electric motor apparatus; it will be understood that where the device is expected to operate continuously for long periods of time and without attention, it is desirable to employ a motor having the low current consumption, constant speed and general dependability characteristic of the patented motor.

Cam 6? is provided, for example, with two oppositely disposed rises or high spots 69, and a pair of normally open cam contacts 10 are arranged to be plosed by each passage of a. rise 69-thus in the instance shown, twice during Cam 68, which may be assumed to rotate at the same speed as cam 61, is provided with a single rise H, which is longer in extent than either rise 69 of cam 61, and which is so disposed that it shifts a contact-operating follower l2 shortly before contacts 10 are closed by one rise'69 of cam 67, and keeps the follower in shifted position until after the same rise 69 (on cam 61) has passed the contacts 10 and permitted them to reopen. When shifted, the follower I2 is adapted to open the normally closed contacts 13 and to close the normally open contacts 14.

One of the input terminals (ii of the horn is connected through conductor to the connection. 16 between the batteries 65 and 66: the other input terminal of the horn is connected through conductor 16a, heavy duty contacts ll (normally open) of the relay 24, to the common contact member 12a of the contacts 13 and 14. The other sides of the contacts 13 and M are respectively connected to the opposite ends of the batteries 65 and 66, and it will now be appreciated that, assuming contacts Tl to be closed, the horn is connected to battery 65 or battery 86 respectively according to whether contacts '13 or M are closed. Furthermore, since the sides of the batteries 65 and 66 which are connected together through the common connection 16 are opposite in sign, the current flow through the horn when contacts 13 are closed is in th reverse direction from the flow when contacts 14 are closed. The

low-current relay 24 is conveniently used to avoid the association of heavy duty contacts with the timing""cam Bl (although in some cases, heavy duty contacts may be used at 10 and the relay 24 omitted), and the winding of the relay may'be connected,- as shown, through contacts 10 to the midpoint 16 of the batteries, and also through the contact arm 12a and selectively through contacts 73 or 74, to the other side or one or the :1 other of the batteries in the same manner as the til-contacts 14 being now closed. The horn continues to blow until the rise 69 passes contacts 10, opening them, thereby de-energizing relay 24 and opening its contacts 11 in the supply circuit to the horn. Thereafter, the follower 12 drops down from the rise H, and contact 13 are closed. They remain closed during the time that the other or opposite rise '69 of cam 61 closes the contacts l0; and it will now be understood that when the contacts 10 are' thus again closed to energize the relay 24 and operate the horn, both the relay and the horn are supplied from battery 65, and current flows through the horn in the reverse dlrection from that during th immediately previous period of energization. In other words, as the motor 23 continues to drive cams 61 and 68, the horn is periodically sounded and the direction of current flow through it is reversed each time, so that wear or other disturbance of the horn contacts 50, particularly as occasioned by transposition of metal between these contacts, is very greatly reduced; the action at the contacts 50 is thus, so to speak, a series of brief tendencies to carry the metal first one way and then back again respectively, so that over a long period of time the contacts are relatively unaffected by metal transposition.

It will be noted that the arrangement of cams 57 and 68 is such that contacts 13 and 14 are operated at times when no current is flowing, so as to avoid wear of these contacts by arcing. At the same time, it will be noted that the program contacts 10 and the heavy duty relay contacts 11 both benefit by the same reversal of current flow which is provided for the horn; in consequence, wear or other deformation of contacts In and 71 is greatly obviated.

It will be appreciated, of course, that the number of rises 69 on cam 61 and correspondingly the use of one or more rises II on cam 68 may be varied to suit requirements of design or operation. In one embodiment of the invention, the arrangement has been that shown in Fig. 5, with the rises 69 of such length, and with the, motor 23 driving the cam 61 at such rate (2 R. P. M.), that the horn makes four one-second blasts each minute; and with continuous operation of that character for a period exceeding six monthsfour blasts per minute, day and nightthere was no appreciable deformation of the contacts 50 and very little appreciable wear.

It will be understood that the capacity of condenser 63 (for ease in mounting, two condensers 63 are shown in Fig. 3 and will be understood as connected in parallel) may be readily selected to coordinate the period of the electrical circuit with the natural period of the mechanical elements.

It will be appreciated, of course, that over longer periods of time, or under conditions requiring a very heavy current through contacts 50, the latter eventually wear down. As a result the space '62 is shortened, and the amplitude of diaphragm vibration correspondingly decreased. Furthermore, over a given period of time the voltage of the supply batteries and 65, may gradually decrease, resulting in a decreased ,current through the horn and likewise a decreased amplitude of vibration, even though'space 62 'remains the same. It is accordingly an important feature of my invention to provide instrumentalities to adjust automatically for these and other variations in amplitudacurrent consumption, or

the like; whereby over even very long periods of time, the amplitude of the,horn may be kept substantially constant, or so controlled as to keep Figure and as previously described. There is also provided a ratchet motor comprising an elec tromagnet having a winding 88 and adapted when energized to attract an armature 8| which thereby shifts a pawl 82 to the left and rotates a ratchet wheel 88 to a predetermined extent corresponding, say, to one or more notches of the wheel.

The ratchet wheel 83 is connected-for example, by gearing or by direct mounting on the same shaftto rotate the worm 55 which in turn, as previously explained, effects adjustment of the anvil member 53 in a vertical direction. For the purposes presently to be described, it will be understood that the operation of the ratchet motor, upon energization of its winding 88, is such as to shift the anvil 53 downward for a predetermined distance upon each energization of the motor.

The apparatus shown in Fig. 6 also includes a spring 85 having one end fixed at a point 88 and having a screw 81 adjustably disposed at its other end in the path of the armature 46 when nals 6|, and at the other side through contacts 8| (normally open, however, when the horn is not in operation), spring 85 and through ground back to the lower of the terminals 6|.

When the apparatus is to'be used, the worm 55 and anvil 53 may first be adjusted manually to provide the. proper amplitude and operative characteristics of the horn as previously described. The screw 81 is also pre-adjusted so Lhat if the desired or any greater amplitude of vibration of the diaphragm 68 is obtained, the

armature 48 will strike the screw 81 for the purposes now to beexplained. Let it be assumed that by virtue of a cycling mechanism (such as in Fig. 5) current is applied to the input termi= nals 6| and the armature 48 is set in vibration. On its first return stroke, or at least, practically immediately after it starts to vibrate, the armature 48 strikes the screw 81 and throws the spring 85 upward so as to close contacts 8| and open contacts 88. Closure of contacts 8| establishes l current fiow through the relay winding 83;wherethe latter moves upwardly on a return stroke.

.To prevent wear, the screw 81 may have a hardened tip and a hardened insert (not shown) may be placed in the upper face of the armature where the latter will strike the screw tip. The

spring 85 may be weighted to make its action more positive and to minimize stray vibration (transmitted, for instance, from the diaphragm when operating), and the screw 81 may be set with the lock nut 88 in any desired-adjusted position relative to the upper surface of armature 46. A pair of contact elements are respectively mounted on opposite sides of the spring, so as to provide, in cooperation with stationary contact elements, a set of contacts 88 closed when the airing is in its normal or unshifted position, and a open; contacts 98 being opened, and contacts 8| closed, when the spring is shifted upwardly. Intermediate the contacts 88 and 8|, and the anchorage' 86, the spring 85 carries an armature 82, adapted to be attracted upwardly by an adjacent electromagnet having a winding 83 and thus providing a lock-up relay for the spring.

The pawl 82 of the ratchet motor has a retracting spring 82a to restore the pawl to its original position upon de-energization of the winding 88, and a releasable check 83a holds the ratchet wheel 83 (and other driven p arts) against any displacement, accidental or otherwise, which is not occasioned by 88.

It will now be understood that the input terminals 6| of the apparatus shown in Fig. 6 may be conveniently connected to a control apparatus for intermittently supplying current to the horn. For example, these terminals may be connected to a cycling and current-reversing arrangement such as shown .in Fig. 5; indeed, in Fig. 6 the horn winding 33 and horn contacts 58 are connected in series across the terminals 6| just as in Fig. 5. The circuit of the ratchet motor windby its armature 82 is attracted and held; and the spring 85 is thus locked in its upper position, by the relay, throughout the interval that the horn is actually in operation. Upon cessation of current supply to the terminals 8|, the relay 88 is de-energized, releasing its armature 82 and restoring the spring 85 and associated parts, in-

cluding contacts 88, 8|, to their original or normal positions. The set of operations Just described is repeated each time the horn is energized, as by the cycling mechanism, and it will now be seen that so long as the horn is working at its full and proper amplitude, the contacts 88 are opened throughout each period of energization, so that the ratchet motor winding 88 is never energized, or never sufliciently energized to set of contacts 8| which are normally operate the ratchet, and in consequence'no adjustment is made of the anvil 53.

If, however, because of wear of the contacts 58,

or because of decrease in battery voltage; or for any other reason, the amplitude of diaphragm vibration is reduced below the desired value, the armature 48 will fail to strike the screw 81 when the horn isturned on, or at least will fail to move the screw sufliciently for operation of contacts 88 and 8| as previously described; that is, the con tacts 88 will remain closed at least long enough to energize the winding 88 and operate the rachet motor. In consequence the ratchet wheel 83 is rotated to the predetermined extent, and the an- V11 53 is.correspondingly adjusteddownward to energization of the winding ing 88 extends from the upper of the terminals through conductor 81 to the upper or the termiwiden the gap 82 and increase the amplitude of horn; vibration as previously explained. It will be understood that unless the one adjustment is sufiicient, the anvil 53 is shifted again, and thus progressively, each time the horn is set in operation by the cycling mechanism, untilthe desired amplitude is re-obtained-i. e., until armature 48 again so strikes the screw 81 as to open the contacts 88 promptly and bring the lock-up relay into play.

Although a supplemental or restoring spring may be provided for the control spring 85, my

present preference is-to employ a magnetic re-' storing or holding arrangement. Thus the weight 88, which may serve to weight the spring (enhancing its momentum, for positive closure of contacts 8| when the armature 48 strikes the screw 81), may be made of ferrous material, and a permanent magnet 88 may be disposed below and in proximity to the weight 98. The magnet thus positively holds the weight 88, and the spring 85, in normal position. but permits ready release of the same at desired times. That is, this magnetic arrangement is substantially unaffected by vibrations which are necessarily present in the effective locked-up condition than would be possible against a restoring spring, which would necessarily have in increased tension in its extended position. The magnet 99 is preferably made of a magnetic alloy that is practically immune to demagnetizing effects of vibration, such as the alloy commercially known as Alnico.

It will now be seen that the described arrangement affords a prompt, eflioient and automatic adjustment of horn amplitude, particularly to restore the latter to a desired value whenever it drops below that value. I

The arrangement shown in Fig. 'l is in general similar to that of Fig. 6, except that the contacts- SI and the lockup relay are dispensed with, and mechanical means are provided for preventing operation of the ratchet motor when the horn is operating at the desired amplitude. To that end, the spring 85 is mechanically connected to the plunger I of a dash pot IOI of the delayed return type, i. e., so constructed as to afford little resistance to upward movement of the spring 85, but to provide a substantial delay or retardation in the return of the spring 85 after it has been moved up.

It will now be seen that if the horn is operated at its full proper amplitude, the spring 85 will, as in the case of Fig. 6, be thrown promptly upward each time current is applied to the horn motor, opening contacts 90 and preventing energization of the ratchet motor. Furthermore, during the remainder of each operating interval of the horn, the dash pot IOI prevents the return of the spring 85 to normal position before screw 81 is struck by the rapidly vibrating armature; that is, the mechanical lag afforded by the dash pot, cooperating with succeeding impingements of the armature 46 on the screw 81, maintains the spring 85 in its upper position. On the other hand, if the amplitude of horn vibration is low, the screw 81 will not be struck by the armature 48, or will not be struck sufliciently to open contacts 90; in consequence the ratchet motor will, as in the case of Fig. 6, be operated one step for each interval of horn energization, until the anvil 53 has been so adjusted as to restore the amplitude of vibration of diaphragm 60 to its desired value.

For variety of illustration, a holding or restoring spring I02 is shown connected to the member 85 in Fig. '7, in lieu of the magnetic arrangement shown in Fig. 6. Although magnetic means are now deemed to be preferable, as explained above, the spring device shown in Fig. 7 is satisfactory in a number of cases.

A somewhat simplified arrangement for automatic amplitude control is illustrated in Fig. 8, wherein the horn armature 46 carries an adjustable striker screw or pin I05 having an insulated tip I06 and disposed so that the latter abuts upwardly against the end of an auxiliary contact spring I01. The latter has an associated set of contacts I08 which are arranged to be opened when the tip of screw I05 strikes the spring m and moves it up. In this arrangement, as in the case of Figs. 6 and '7, the connections of the horn motor and its attendant cycling mechanism through terminals 6| may conveniently be assumed to be the same as shown in Fig. 5. The winding of the ratchet motor is connected at one side through contacts I08 to the upper of the input terminals 6 I, and at the other side through ground to the other of the input terminals.

Assuming that the horn has been otherwise adjusted to obtain the proper-amplitude of diaphragm vibration, the screw I05 is adjusted so that when the horn is thus properly operating, contacts I08 are opened during at least a substantial part of the upper half of each cycle of vibration of the horn diaphragm and armature assembly. Under those circumstances, the circuit of the ratchet unotor winding 80 is rapidly interrupted, preventing sufficient flow of current to operate the ratchet motor, and thereby preventing displacement of the anvil 53. However, if the amplitude of horn vibration decreases below a value predetermined by the adjustment of screw I05, the latter will no longer provide the normal intermittent opening of contacts I08 during intervals of horn energization, and the ratchet motor will thus receive sufficient. current to operate it during each such interval. That is, as before, the ratchet motor then operates one step for each such interval of horn energization, until the anvil 53 has been so adjusted as to restore the desired amplitude of horn vibration;

The arrangement of Fig. 9 is found similar to that of Fig. 8, except that further instrumentalities, including a sensitive relay, are provided for more accurate and dependable operation, and particularly for avoiding any disadvantage due to wear or pitting of the contacts I08 in Fig. 8, The winding IIO of the sensitive relay thus provided in Fig. 9 is connected at one side through the contacts I08 to the upper of the input terminals GI and at the other side through ground to the other of the input terminals. The armature III of the sensitive relay is adapted in its retracted position (as shown) to close a pair of contacts H2, and in its attracted or upper position, to close a pair of contacts H3. The contacts I I3 are connected in parallel with the contacts I08 so as to provide a stick circuit for the relay when the latter is energized by a relatively momentary closure of contacts I08. The circuit of the ratchet motor winding 80 extends at one side through contacts I I2 to the upper of the input terminals 6 I, and at the other side, through ground to the other of the input terminals.

The striking screw or pin I05 is adjusted in generally the same manner as for the arrangement of Fig. 8 and it will now.be appreciated that when the horn is vibrating at true or proper amplitude, the spring I0! is promptly shifted up at the starting of each interval of horn energization. As soon as contacts I08 are thus closed, the sensitive relay H0 is promptly energized: attracting its armature III; opening contacts II2 so as to prevent flow of current to the r ratchet motor and to prevent operation of the latter; and closing contacts II3 of the stick circuit sothat the relay 1 I0 remains energized until current supply is discontinued from terminals 6| by the cycling mechanism. If the amplitude of horn vibration, however, drops below a predetermined value, the contacts I08 will not be closed or will not be sufficiently closed to operate the relay II 0; in consequence, contacts II2 remain closed and the ratchet motor operates to adjust the anvil 53 one step. As before. sue

cessive steps of adjustment are made. if necessary, for each interval of horn energization until the desired amplitude is re-obtained.

It will be appreciated that in this arrangement the ratchet motor is positively locked out of circuit at times when there is sufficient amplitude of horn diaphragm vibration. At the same time, contact wear is practically eliminatednot only because the current drawn by the sensitive relay may be much less than that required to operate the ratchet motor (with respect to contacts I08, in comparison with Fig. 8), but also because current flow through contacts I08 need be merely established at the start of each interval of horn energization (under normal conditions), by virtue of the immediately following closure of the stick circuit contacts I I3. Furthermore, by virtue of the locked-up arrangement of the relay I I0, such frying of the ratchet motor contacts (here contacts H2 in lieu of contacts I08 of Fig. 8), as

might be occasioned by vibrations existing in the horn, is eliminated-except, of course, during periods of low amplitude when such vibrations are at a minimum, Moreover, the inclusion of a sensitive relay, such as relay III), generally permits finer and more accurate adjustment, since the only frictional load of this relay is the small constant load of operating its contacts; whereas when the ratchet relay 80 is operated directly, the quality of adjustment may be somewhat inferior since its frictional load (of ratchet and attendant instrumentalities) may vary.

Fig. 10 illustrates a somewhat different form of amplitude control arrangement, but including a ratchet motor or like device corresponding to that shown in Figs. 6 to 9. The armature 46 of the horn motor carries a strip I of ferrous material, having a winding IZI and disposed in proximity to the poles of a permanent magnet I22 (preferably made of the same material as magnet 89 in Fig. 6, for the same reasons) so that when the armature 46 vibrates, alternating electro-motive force is induced in the winding MI. The latter is connected through a suitable rectifier I23for example, a plurality of small copper oxide rectifier-elements connected in the usual bridge connection for full wave rectification-to the winding I24 of a sensitive D. C. relay. It will here be understood that in some cases, a suitable alternating current relay of sensitive type may be employed, eliminating the necessity for a rectifier.

For convenience of illustration, the cyclingmechanism is' shown in more simplified arrangement than that of Fig. 5, and without the cur-, rent-reversing means; but it will be understood that the latter may, if desired, be readily and advantageously included in the apparatus of Fig.

10. As. shown in Fig. 10, the program cam I21,"

associated with the cam I21, to be operated by the same follower I; these contacts I33'may conveniently have a relatively large gap or be otherwise so arranged as to close only when the follower I30 is lifted to the upper surface I32 01 the rise. The sensitive relay I24 has a pair of normally closed contacts I35 which are adapted to be opened by the relay armature upon sufllcient energization of the relay winding; the relay armature being provided with an adjustable holding or restoring spring I36 so that the relay ground to the other side of the battery.

It will now be appreciated that the sensitive relay is preferably so adjusted, as by its spring I36, that when the horn is operating at the full desired amplitude, just enough current is induced in winding IN and supplied to the relay winding I24 to open the contacts I33, and keep the same open while the horn'is actually operating. Thus let it be assumed that the program cam I27 is rotating clockwise and that the follower I30 rides up on the lower part I SI of the rise I28. Contacts I29 now close, establishingcurren t flow to the horn motor and setting the horn in operation. At this time, however, no current can flow to the winding 30 of the ratchet motor, since contacts I33 are still open. After a time, usually short, but sufiicient to allow the horn to build up to its full amplitude of vibration, the follower I30 is lifted to the upper part I32 of the rise I28.

The horn continues in operation, since contacts I29 are still'closed; but at the same time contacts I33 are closed in the circuit of the ratchet motor winding 00. crating at its full desired amplitude, the electromotive force induced in winding I2i has already operated the senstive relay, 1. e., its contacts I33 have been opened before contacts I33 were closed by the cam; and current from winding I2I continues to keep the contacts I35 open as long as the horn remains in operation at full amplitude.

On the other hand, if the amplitude of horn vibration is below the desired value, or if the horn is undesirably slow in building up to the intended amplitude, the sensitive relay is insuiiiciently energized to open its contacts I35 and in consequence current flows through the winding 00 of the ratchet motor, causing a single step operation of the latter as before.

When the follower I30 reaches the end of the rise I28, both contacts I28 and I33 are opened, respectively turning off the horn and preventing or interrupting current supply to the ratchet motor. Thus, if the horn amplitude is correct,

vpittingorother,injury of the contacts I35 and I33, since the normal opening of the former will no adjustment is made; but if the amplitude has unduly decreased, the ratchet motor will be brought into operation. during each interval of horn energization so as to shift the anvil 53 downwardly one step, so to speak, until the amplitude of diaphragm vibration is restored to its desired value.

It will be noted that thelarrangement shown in Fig 10 permits the horn motorato reach its full amplitude of vibration before current can he applied to the ratchet winding thus insuring a positiveoperation of relay I24 before the end of that preliminary interval, if the horn amplitude is proper; and at the same time preventing If, however, the horn is 010-.

be during that preliminary interval, and the only times that the latter are called upon to make and break a current flow are the periods of actual amplitude correction. In some cases, however, the delayed operation obtained with contacts I33 may be dispensed with-since the heavy ratchet relay 80 is usually slower-acting than relay I24-- although there will then usually be some current flow through contacts I35 each time they open.

Where a sensitive control relay is usedsuch as relay H in Fig. 9 or relay I24 in Fig. 10- it may be desirable to mount the same (suitably enclosed) out of the horn housing and apart from it, to avoid the disturbing eifects of vibration on the relay and thus to permit greater sensitivity of adjustment.

Figs. 11a and 11b show a somewhat modified arrangement of certain instrumentalities in Fig. 10.

In Fig. 11a the horn armature 46 carries and vibrates a supplementary soft iron armature I42, which thus moves within a winding I43, the vibration being in a direction perpendicular both to the plane of member I42 and to the axis of the winding. A U-shaped permanent magnet I44 is provided (see also Fig. 111)) having inwardly extending projections disposed alongside of the winding, the arrangement being such that one pole I45 (say, the north pole) of the magnet has a projection I46 extending along one side of the winding I43 at the top, and another projection I4'I extending along the other side of the winding at the bottom, While the south pole I48 of the magnet has corresponding projections along the winding, oppositely arranged-only one of such projections I49 being visible in Fig. 11b, beside the winding at its top and opposite the projection I46. in the winding, moves first toward a pair of magnet poles arranged, for example, with the north pole near the end-of the armature and the south pole toward the center, and thereafter moves back toward a set of magnet poles oppositely arranged with respect to the armature. Hence as the armature approaches first one set of poles and then the other, electromotive forces will be induced in successively opposite directions in the winding I43; that is, there is a complete reversal of flux as the armature moves, say, from its lower to its upper position, as seen in Figs. 11a and 111).

It will be understood that the arrangement just described may be substituted for the parts I-l22 in Fig. 10, the winding I43 being connected in lieu of the winding I2I in Fig. 10. In-

deed, the structure of Figs. 11a and 11b is at pres-,

ent preferred, since it may afford a greatly increased flow of current to the sensitive relay, and

Thus the armature I42, as it vibrates withcause wear of the contacts 50 has reduced the time of energization of winding 33 in each vibratory cycle (thus reducing the horn amplitude), or because the voltage of the supply battery I52 has dropped (likewise reducing the horn ampli- 'tude)the contacts I5I will remain closed during each interval of horn operation and effect a step of ratchet motor operation, as in Figs. 6 to 10.

A presently preferred arrangement for controlling the instrumentalities just described includes a program cam I53, corresponding to the cams I21 and 61 of Figs. 10 and 5, respectively, and provided with a rise having at least two levels, via, a preliminary low level I54 and 'a subsequently advanced, higher level I55. A set of contacts is arranged to be operated by a follower I58 as follows: normally open contacts I51 are adapted to be closed when the follower I56 rides up on either level of the cam rise; contacts I58, normally closed, are adapted to be opened some time after closure of contacts ISIS-say, when the follower reaches the highest spot or level I55 of the cam; and contacts I59, normally open, are adapted to be closed'only when the follower I56 is on the high spot I55. As will be seen, the circuit of the horn motor is from one side of the battery I52, through contacts I5'I (when closed), through relay winding I50 (except when shorted by closure of contacts I58), and through horn winding 33, contacts 50, and back through ground to the other side of the battery. The circuit of the ratchet motor is from one side of the battery through contacts I51 and I59 (when both are closed), contacts I5I, conductor I60, winding 80, and back through ground to the other side of the battery. The normally closed contacts I58 are connected across relay-winding I50 to short circuit the latter except at desired times as will presently be explained.

Assume now that the cam I53 is rotated until the follower I56 rides up on the low spot I 54. Contacts I51 now close, initiating an interval of horn energization. At this time relay I50 is short circuited, and current is prevented from flowing through the ratchetmotor winding 80 because the latter may thus be more accurately adjusted for selective response; it being particularly noted that the structure of Figs. 11a and 11b provides a more eflicient generator in that it produces a much greater change of flux, including a complete reversal of flux for each cycle of vibration. The apparatusshown in Fig. 12 represents a still further modified system of automatic adjustment of horn amplitude, and here, as in Fig. 10,

the circuit and arrangement of the cycling mech contacts I50 are still open. After the preliminary high surge of current through the horn has subsided to normal flow, the follower I56 rides up on the high spot I55. Contacts I51, of' course, remain closed and the horn remains in operation. Contacts I58 open (as hereinafterstated, preferably prior to the closure of contacts I59), thereby inserting the relay wlnding I50 in series with the horn. If the current through the horn is now at its proper desired value, the relay is sufiiciently energized to open its contacts I5I so that no current can flow through the ratcheigl motor winding 80. On the other hand, if the horn driving current is low, as for either of the reasons, mentioned hereinabove, or for any other reason,

the relay I50 will not be sufliciently*,'energized to open its contacts I5l; and since'corita'cts I59 are now closed by the high spot I55, cu rren't willbe anism is shown in simplified form; it being understood that if desired, control apparatus of the type shown in Fig. 5, may be readily and advantageously included. The apparatus of Fig. 12 com-'- prises the horn and ratchet motor for adjustment of anvil 53, as previously described. The wind ing I50 of a series relay is arranged to be consupplied to the ratchet motor winding 80. The

ratchet motor thus effects one step of adjustment of the anvil 53; and as before, the horn may thus be progressively adjusted, step by step, during succeeding intervals of energization, until its current is brought up to the desired value corresponding to full amplitude.

As mentioned, horns of the we here described are apt .to draw an abnormally heavy current when power is first applied and for an extremely small fraction of a second thereafter, but this current is promptly reduced to normal value by the counter electro-motive force of the horn motor, during normal operation. It will thus be seen that the control afforded with contacts 56 to I59 and the associated ins'trumentalities prevents a false operation of relay I50 which might be occasioned by the heavy preliminary current at times when the normal horn-driving current is too low and adjustment of the'horn is actu ally desired. As will now be readily understood, the contacts I55, l! and I58 may easily be so adjusted in relation to each other-that the series relay Iii] will attract its armature (and open. contacts l5i), or will be given the oppo tunity to attract its armature, before current is applied to the circuit of its contacts ISI; for example, the arrangement is preferably such that before contacts I59 close, contacts 58 open for a sumcient time to provide for operationof the relay I513 and thereby avoid such wear of the relay contacts I5l as would be occasioned if they were opened when current was actually starting to flow through them to the winding 80.

Although in Figs 6 to 10 and 12 a simple step- .by-step ratchet motor is illustrated for operation of the adjusting worm 55, other devices may be used in some cases, such as a rotary motor conveniently geared down to drive very slowly, or a operation of my invention, together with the apparatus which I now consider to represent the best embodiments thereof, but I desire to have it understood that the apparatus disclosed is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and others omitted and some of vibratory motor having self-interrupting sec-- ondary contacts. Apparatus of the type illustrated is at present generally preferred, however, since the horn is usually intermittently operated and the program mechanism, therefore, conven iently furnishes the necessary impulses for oper ation of a ratchet motor or the like. Furthermore, in ordinary circumstances, only very mi= nute increments of adjustment are desired and the same may be efiectively and economically obtained with the type of motor illustrated.

It will now be appreciated that the present invention not only afiords a horn which is relatively simple in construction, demndable in UP? eration, and easily built, to have any predetermined pitch within a wide range, but also adords distinctively improved control arrangements for such horns so as to avoid contact wear and impairment of normal operation and also to pro vide for effective automatic adjustment of the horn to keep it at a normal standard of operation throughout a long period of time. The adtive inobviating or minimizing the wear or other derangement which would otherwise inevitably result from the strenuous operating conditions just described. r

In accordance with the provisions of the patent statutes, I have herein described the principle of vantages realized by the invention are, further-- more, of special importance where the signal de every day. The invention is particularly eiiecthe features of each modification may be embodied in the others without interfering with the more general results outlined, and the invention extends to such use within the scope of the appended claims.

I claim:

1. The combination with sound signal apparatus comprising an armature and electromagnetic means for efiecting vibration thereof, of means for maintaining production of a sound signal ofhigh amplitude, comprising means for adjusting the amplitude of vibration of said armature, and means responsive to variationin said amplitude of vibration and including control means operated by the armature, for operating said adjusting means to restore said amplitude of vibration to a predetermined value.

2. In sound signal apparatus, in combination, an armature and driving means therefor comprising an electromagnet and make-and-breal; contacts in series with the same and associated with the armature for causing vibration of the latter toward and away from the electromagnet, one of said contacts being carried by the arma= ture and the other contact having a supporting spring for maintaining the contacts closed during a substantial part of each cycle of vibration, and anvil means adjustably disposed for abutment by ,said supporting spring, whereby the interval of contact closure during each cycle may be adjusted, as desired, said anvil means comprising a worm gear having a transverse face disposed for direct abutment by said spring, a fixed support, a

shaft for said gear threaded in said support, and

a worm engaging the gear for rotating the gear and thereby rotating said threaded shaft to ad just the position of said spring-abutting face axially of the shaft.

3. In electric sound signal apparatus, in com== bination, a vibrating member, means for ad justlng the amplitude of vibration thereof, and means responsive to variations in amplitude of vibration of said member for operating said adjusting means to restore said amplitude to a predetermined value.

4. In electric sound signal apparatus, in com= bination, a vibrating member, means for adjusting the amplitude of vibration thereof, a member disposed in the path of said vibrating member for-displacement thereby, contacts associated with said last mentioned member and adapted to be opened upon displacement of said member when the vibrating member is operating at a predetermined normal amplitude, and means energized by closure of said contacts to operate theadjustingmeans when the amplitude of vibration of the first mentioned member is less than a predetermined value.

5. In sound signal apparatus, in combination, an electrically driven vibrating member, means for adjusting the amplitude of vibration thereof, means normally biased to operate said ad justing means in a direction to increase said amplitude of vibration, and means controlled by said vibrating member and responsive to the amplitude of vibration thereof, for preventing operation of said last-mentioned means when the amplitude of vibration is above a predetermined value.

6. In sound signal apparatuain combination, electrically actuated vibrating means, means for intermittently supplying energy to said vibrating means to operate the same during the intervals of energy supply, means for adjusting the amplitude of vibration of said vibrating means, means having an energy supply circuit and normally biased to operate said adjusting means during each interval of energy supply to the vibrating means, and means responsive to the amplitude of vibration of said vibrating member for opening said supply circuit during each interval of energy supply to the vibrating means, at times when the latter is vibrating at more than a predetermined amplitude.

7. The combination of claim 6, in which the last-mentioned means includes a pair of contacts in the aforesaid supply circuit, control means displaced by said vibrating means upon each initiation of vibration thereof, to open said contacts when the vibration has more than a predeter mined amplitude, and lock-up relay means including an armature associated with said control means, for keeping the contacts open until the end of the interval of energy supply to the vibrating means.

8. The combination of claim 6, in which the last-mentioned means includes normally closed contacts in the aforesaid supply circuit, means shifted by initial vibration of said vibrating member to'open said contacts only when the amplitude of vibration is more than a predetermined value, and retaining means responsive to shift of said last-mentioned means for preventing closure of said contacts until the end of the interval of energy supply to the vibrating means.

9. The combination of claim 6, in which the last-mentioned means includes relay means, circuit controlling means operated upon initiation justing means during each interval of energy supply, means operated by said vibrating means for setting up an electromotive force in accordance with the amplitude of vibration thereof, re-

I lay means energizable by said last-mentioned of vibration of said vibrating means to energize said relay means when the amplitude of vibration is above a predetermined value, circuit-controlling means responsive to energization of the relay means for opening the aforesaid supply circuit and for keeping said relay means energized until the end of the interval of energy supp y to the vibrating means.

10. In sound signal apparatus, in combination, a vibrating member, means for adjusting the amplitude of vibration thereof, means controlled by said member for setting up an electromotive force variable in accordance withthe amplitude of vibration of the membenand means controlled by said electromotive force, for operating the adjusting means when the electromotive. force is below a predetermined value.

11. The combination of claim 10 wherein the last-mentioned means is adapted for control by an alternating electromotive force, and wherein the means for setting up an electromotive force comprises an armature vibrated by the vibrating means and a field winding disposed for induction of alternating electromotive force therein upon vibration of said armature. M

12. In electric sound signal apparatus, in combination, electrically driven vibrating means, means for intermittently supplying energy to said means to operate the same during the intervals of energy supply, means for adjusting the amplitude of vibration of said vibrating means, means energizable by said energy supplying means and normally biasedto operate said, ad-

means when the electromotive force has more than a predetermined value, for preventing operation of the means for operating the adjusting means, and circuit controlling means associated with the intermittent energy supplying means for maintaining the adjusting means inoperative during a preliminary portion of each interval of energy supply, to delay controlling action of the relay means until the vibrating means has built up its full amplitude of vibration.

13. In sound signal apparatus, in combination electrically driven vibrating means, means for adjusting the amplitude of vibration thereof, a current supply circuit for said vibrating means, and means associated with said circuit and responsive to variations in current consumption by said vibrating means, for operating the adjusting means in a direction to increase the ampli tude of vibration when the current consumption is less than a predetermined amount.

14. In electric sound signal apparatus, in com-'- bination, a vibrating member, electrically actuated driving means therefor, including means for successively making and breaking current supply to said driving means for effecting vibration tion, and means responsive to variations in current consumption by said driving means for operating said adjusting means to restore the current consumption to a predetermined value.

15. In sound signal apparatus, in combination, electrically driven vibrating means, means for adjusting the amplitude of vibration thereof, means for intermittently supplying energy to said vibrating means to operate the same during the intervals of energy supply, actuating means biased to operate said adjusting means in a direction to increase the amplitude of vibration during each interval of energy supply, and control means responsive to variations in the current consumption of said vibrating means, for preventing operation of said actuating means when said current consumption is above a pre-.

determined value.

16. The combination of claim 15, which also includes supplementary means associated with the intermittent energy supplying means, for keeping both the actuating means and the current-responsive control means inoperative during a preliminary portion of each interval of energy supply, to,prevent any false operations occasioned by preliminary energy surge to the vibrating means. m

17. In sound signal apparatus, in combination, means to be vibrated for production of sound, electrically actuated driving means therefor, including control means for successively making and breaking current supply to said driving means at, the desired frequency of vibration, ad-

justing means associated with said driving means current to operate the same during the times of.

connection, and means brought into play when the intervalsof current supply by the control means have less than a predetermined duration,

for causing said adjusting means to operate to a predetermined extent in each successive time of current; supply by the switch means, until the aforesaid intervals of current supply are restored to the aforesaid predetermined duration.

18. An automatic electric fog horn, comprising in combination, means 'to be vibrated for production of sound, electrically actuated driving means therefor, means for adjusting the amplitude of 1 vibration of said first mentioned means, means for intermittently supplying energy to said driving means to operate the first mentioned means during the intervals of energy supply, and means responsive to variations in amplitude of vibration of said first mentioned means for progressively operating said adjusting means during successive intervals of energy supply, until said amplitude is restored to a predetermined value.

19.. In sound signal apparatus, in combination, a vibrating member, electromagnetic means controlled by said member for generating an alternating current in accordance with the amplitude of vibration of the member and including a winding and means for creating a reversal of flux through said winding in each cycle of vibration of the member, and means controlled by said electromagnetic means and in response to said alternating current, for adjusting the amplitude of vibration of the member.

20. The combination of claim 19 in which the electromagnetic means includes an armature car- JOHN R. MACKAY. 

